diff --git a/src/google/protobuf/message.cc b/src/google/protobuf/message.cc
index 2cf07dbdf4..eb81694daf 100644
--- a/src/google/protobuf/message.cc
+++ b/src/google/protobuf/message.cc
@@ -188,13 +188,7 @@ size_t Message::MaybeComputeUnknownFieldsSize(
 }
 
 size_t Message::SpaceUsedLong() const {
-  auto* reflection = GetReflection();
-  if (PROTOBUF_PREDICT_TRUE(reflection != nullptr)) {
-    return reflection->SpaceUsedLong(*this);
-  }
-  // The only case that does not have reflection is RawMessage.
-  return internal::DownCast<const internal::RawMessageBase&>(*this)
-      .SpaceUsedLong();
+  return GetReflection()->SpaceUsedLong(*this);
 }
 
 static std::string GetTypeNameImpl(const MessageLite& msg) {
diff --git a/src/google/protobuf/message.h b/src/google/protobuf/message.h
index 47f41b89ec..83ba793e93 100644
--- a/src/google/protobuf/message.h
+++ b/src/google/protobuf/message.h
@@ -286,7 +286,8 @@ class PROTOBUF_EXPORT Message : public MessageLite {
   void DiscardUnknownFields();
 
   // Computes (an estimate of) the total number of bytes currently used for
-  // storing the message in memory.
+  // storing the message in memory.  The default implementation calls the
+  // Reflection object's SpaceUsed() method.
   //
   // SpaceUsed() is noticeably slower than ByteSize(), as it is implemented
   // using reflection (rather than the generated code implementation for
@@ -296,7 +297,7 @@ class PROTOBUF_EXPORT Message : public MessageLite {
   // Note: The precise value of this method should never be depended on, and can
   // change substantially due to internal details.  In debug builds, this will
   // include a random fuzz factor to prevent these dependencies.
-  size_t SpaceUsedLong() const;
+  virtual size_t SpaceUsedLong() const;
 
   [[deprecated("Please use SpaceUsedLong() instead")]] int SpaceUsed() const {
     return internal::ToIntSize(SpaceUsedLong());
@@ -1572,12 +1573,6 @@ bool SplitFieldHasExtraIndirectionStatic(const FieldDescriptor* field) {
   return ret;
 }
 
-class RawMessageBase : public Message {
- public:
-  using Message::Message;
-  virtual size_t SpaceUsedLong() const = 0;
-};
-
 }  // namespace internal
 
 template <typename Type>